Do you have a Mac running 10.5? If so, see if you get frequent crashes on it. Snow Leopard had issues with certain fonts and font suit cases from what I've read here in the forum. If it runs reliably on 10.5, it's possible that this may be the cause of your trouble.
Running Mac OSX 10.6.5, so I tried changing the fonts. I tried Ariel, Verdana, and Times New Roman - FM continued to crash after each change.
Thank you for your posts.
If you have found the solution, please post here. Otherwise, have you verified all the fonts in your system are not corrupt? Have you tried removing all fonts and reinstalled from the system CD?